So here's the question, I use Scion of Vitu-Ghazi then later on create a token copy of it and returned the first to my hand then played it, would I be able to populate the copy over and over with the new populated copies?
No. The trigger only goes off for a Scion that was cast from the hand. A populated token isn't cast, so the triggered ability of the new Scion token doesn't trigger. You can only get one additional Scion token off the actual Scion that you've cast, by populating the old Scion token with its trigger.
No, a Scion of Vitu-Ghazi's ability triggers only when this very Scion enters the battlefield, if this very Scion was cast from your hand. A token copy will not have been cast from your hand, so its ability won't trigger. The fact that the Scion card was cast from your hand won't help, it's not something that's copiable, it's something that needs to be true for the present Scion of Vitu-Ghazi object that would trigger.
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